It is often necessary to couple together the end of a pipe, such as a water pipe, to another member, such as another pipe, a valve, a fitting, or other similar pipe-like structure. In some cases, the ends of two adjacent pipes may be flanged, and the flanges can be placed into confronting relationship to facilitate bolting the pipes together. This coupling arrangement, however, is not always feasible or available.
A coupling device known as a mechanical joint can be used where one of the pipes does not have an available flanged end. In that situation, the end of the non-flanged pipe is telescopically received into a flared end of a flanged member, with a follower ring situated over the pipe adjacent to the flange. A gasket is provided which is compressed into the pipe surface and against the flare of the other member to create a water-tight seal as the follower ring is bolted to the flange. An exemplary mechanical joint is the Standardized Mechanical Joint (SMJ), which is described in ANSI/AWWA (American National Standards Institute/American Water Works Association) C111/A21.11.
Mechanical joints are suitable for a number of situations, but may not be able to retain a water-tight connection between the pipes when the pipes are subjected to hydraulic thrust forces which tend to cause the pipes to telescope apart, such as pipes utilized in pressurized municipal and industrial water systems. To reduce the risk of such pipes coming apart, pipe joint restraints may be utilized with mechanical joints or other joints. An exemplary pipe joint restraint is illustrated in FIGS. 1 and 2. The end 12 of a first pipe 14, such as a water main pipe, is secured by the pipe joint restraint 16 to the end 18 of a second pipe-like member 20 which may be, for example, another water main pipe or a pipe-like extension of a valve, fitting, fire hydrant, or other similar structure. The pipe joint restraint 16 has an annular retainer gland 22 that is disposed on the outer surface 28 of first pipe 14. The annular retainer gland 22 defines a pipe receiving space 24 therethrough and has an axial centerline 26. The illustrated annular retainer gland 22 includes a front projecting rim 30 which butts up against an annular sealing member 32, such as a gasket, received on outer surface 28 of the first pipe end 12.
The end 18 of the second pipe 20 is flared as at 34 to telescopically receive the first pipe end 12 therein. The flange 36 of pipe end 18 may be secured to the annular retainer gland 22 with T-bolts 38 (only one shown) received through axially-extending holes 40 and 42 on the gland 22 and flange 36, respectively. The gasket 32 is in a recess 44 that is coaxial with the flange 36 and is sized to receive a portion of rim 30 so as to push the gasket 32 into a water-tight sealing relationship with pipe surface 28 and pipe recess 44 as the T-bolts 38 are tightened down.
The annular retainer gland 22 is secured to the first pipe 14 by one or more pipe restraining mechanisms 50. Each pipe restraining mechanism 50 includes a pocket 60 and a pipe engaging assembly 62 cooperatively coupled to pocket 60. Each pipe engaging assembly 62 includes at least one tooth 75 supported on a gripping element 76, an adjustment member 78, which may be in the form of a bolt, and a nut 80 to receive torque to adjust the bolt. A rotation of the bolt 78, such as via nut 80, causes the gripping element 76 to move radially toward or away from the pipe surface 28, depending on rotational direction. The tooth 75 is configured to engage the pipe surface 28 when the gripping element 76 is moved toward the pipe 14, and to thereafter bite into the pipe surface 28 in response to thrust forces tending to move the pipe ends 12, 18 telescopically apart along the centerline 26. The tooth 75 and groove formed thereby resist the tendency of the pipes to move away from the each other.